Thermal switches having a temperature-sensitive pellet and a sliding, star-shaped, contact disk, in which the sliding disk moves away from an electrical lead mounted in a ceramic bushing to break the electrical connection when the pellet melts, are disclosed in U.S. Pat. No. 3,180,958. In the thermal switches of this type in general use today, the body of the electrical lead extending through the ceramic bushing is smooth and it is retained in the ceramic bushing by a sealing resin within the bore of the ceramic bushing and extending out over the outer surface of the bushing around the lead. Electrical connection is normally made through the lead extending through the ceramic bushing which contacts the sliding disk. The sliding disk in turn contacts the wall of the tubular metal casing of the switch and the electrical connection is continued out through an electrical lead connected to the casing. When an over-temperature condition arises, the fusible pellet melts and a spring moves the sliding disk away from its contact with the electrical lead to break the electrical circuit. Such thermal switches are used, for example, in home coffee-making units now in wide use.
It has now been found that when a home appliance containing such a thermal switch overheats, causing the switch to open, the home handyman will often attempt to fix the appliance himself. In doing so, he may push and twist the electrical lead extending through the ceramic bushing and break loose the resin bond between the smooth-bodied electrical lead and the ceramic bushing. Once the resin bond is broken the electrical lead can be moved axially to make contact with the sliding disk and thus remake the electrical circuit, but without solving the problem in the appliance which caused the over-temperature condition in the first place. There no longer being a thermal switch in the circuit, the over-temperature condition can now reoccur and worsen to cause a fire.